The present invention relates to an oscillation driver circuit, an oscillation driver device, a physical quantity measurement circuit, a physical quantity measurement device (e.g., vibrating gyrosensor), an electronic instrument, and the like.
Gyrosensors are classified as a rotating gyrosensor, a vibrating gyrosensor, and the like depending on the method of detecting the force applied to an object. In particular, a vibrating gyrosensor is considered to be advantageous for reducing size and cost from the viewpoint of the constituent elements and the like.
A vibrating gyrosensor that detects an angular velocity causes a physical quantity transducer (vibrator) to produce driving vibrations in a specific direction. When an angular velocity is applied to the vibrator, a Coriolis force occurs perpendicularly to the driving vibrations to produce detection vibrations. Since the detection vibrations occur perpendicularly to the driving vibrations, a detection signal (signal component due to the detection vibrations) differs in phase from a drive signal (signal component due to the driving vibrations) by 90 degrees. The detection signal can be synchronously extracted (detected) separately from the drive signal utilizing the above phenomenon, for example.
A reduction in size and an increase in reliability of vibrating gyrosensors can be achieved using a crystal vibrator.
A vibrating gyrosensor is used in a wide variety of applications, such as shake detection utilized for a video camera or a digital camera, positioning using the global positioning system (GPS) utilized for a car navigation system, and aircraft or robot position detection.
A vibrating gyrosensor is normally driven by a battery. Therefore, it is necessary to increase the life of the battery by reducing the power consumption of the vibrating gyrosensor as much as possible. Accordingly, it is important to thoroughly reduce the power consumption of the vibrating gyrosensor.
Since a reduction in size is strongly desired for electronic instruments (e.g., video camera and digital camera), it is important to reduce the size of a vibrating gyrosensor.
A related-art vibrating gyrosensor drives a vibrator using a sine-wave signal with a given frequency, for example. Since the gain (loop gain) in the oscillation loop must be controlled to be unity in order to maintain oscillations, a gain control amplifier (GCA) is provided in the oscillation loop.
A synchronous detection process is performed to remove noise (e.g., a leakage component of a drive signal of the vibrator) superimposed on a detection signal obtained from the vibrator. The synchronous detection process requires a synchronous detection reference signal. The synchronous detection reference signal is a rectangular-wave signal.
A gain control amplifier (GCA) and a circuit (e.g., comparator) that generates a rectangular-wave synchronous detection reference signal are separately provided (i.e., independent circuits) (see JP-A-10-232132 and JP-A-2006-10408, for example).
The circuit area and power consumption can be reduced by forming the gain control amplifier (GCA) and the amplifier circuit (e.g., comparator) that generates the synchronous detection reference signal using a common circuit.
However, since different characteristics are required for the gain control amplifier (GCA) that adjusts the voltage amplitude of a sine-wave signal and the circuit (e.g., comparator) that generates the rectangular-wave synchronous detection reference signal, these circuits cannot be formed using a common circuit.
When forming the vibrator using a rock crystal with a high Q value and hermetically sealing the vibrator in a package, the driving Q value of the vibrator increases to a large extent. Therefore, the time (startup time) elapsed until a signal from the vibrator is stabilized increases when causing the vibrator to produce driving vibrations.
In order to reduce power consumption, it is preferable to suspend the operation of an unnecessary circuit when a physical quantity such as an angular velocity need not be detected (i.e., provide a low power consumption mode). In this case, a quick transition to a normal operation must be taken into consideration. In particular, when using a crystal vibrator, it is considerably difficult to achieve a quick transition to a normal operation due to an increase in startup time.
Moreover, it is necessary to prevent a situation in which the vibrator breaks down due to an overcurrent in the low power consumption mode and the normal operation mode.